One of the most interesting energy-dependent processes is that which allows cellular accumulation of certain vital ions such as Na ion, K ion calcium against their electrochemical gradient. However, the control of this function, and the nature of energy transduction to the ion is incomplete and lacks the most important part-namely how the energy is tranduced to a movement of ions. The present picture is that ions cause membrane bound enzymes to hydrolyze ATP, which then results in the movement of the ion. The hydrolysis of ATP by Mg ions-dependent Na ion plus K ion-ATPase is controlled by Mg ions, Na ion, and K ion. The energy released from hydrolysis is then transferred in some unknown manner to the sodium for its transport. Data are not available to the nature of ion transporting site per se and its interaction with the hydrolytic site. Our recent studies with plasma membranes of the electric organ of the eel indicated that a Na ion-dependent ionophore is an integral part of Na ion plus K ion-ATPase and part of the Na ion-active transport machine. In another project we have also shown that a Ca ions-dependent and selective ionophore as a part of Ca ions plus Mg ions-ATPase of rabbit white skeletal muscle. Thus, our proposed project will study in detail the molecular mechanism of active transport and in particular the ionophoric site and its relation to the overall pump system. Goals set for the current year are 1) isolation and purification of single small peptide fragment from the small polypeptide of Na ion plus K ion-ATPase; 2) to test the large polypeptide of Na plus K-ATPase for any ionophoric ability such as K ion; 3) to determine the role of Mg ions, Na ion, K ion, ATP and Ca ions on the Na ion-dependent ionophore in changing and regulating the conductance of black lipid membranes.